Bizarre work rules that limit the duties required of school custodians have proven longer lasting than the Energizer bunny — surviving despite decades of criticism and heated City Council hearings.

Among the controversial provisions to survive the latest custodial union’s contract is one that limits the painting of buildings to 20 percent of what’s required and of walls “to the height of 10 feet.”

Another rule limits how many tiles a custodian can replace per month, setting a cap as low as 75 and as high as 200.

“I labeled it 30 years ago a permanent scandal, and it’s still a permanent scandal,” said John Fager, a Manhattan public high-school teacher who advised the City Council president on the issue in the 1980s.

“If you want a title for the contract, it’s ‘It’s not my job unless you pay me more,’ ” he added.

Officials at Local 891 of the International Union of Operating Engineers, which represents more than 800 custodial engineers, did not return a call seeking comment.

School custodial staffers insist that only a small minority of custodial engineers take advantage of the lax work rules — and that the majority works hard and applies common sense.

“While the contract states that the staff only paint up to 10 feet high, we always painted everything anyway,” said Ron Glinski, a former custodial staffer at IS 34 on Staten Island. “When windows are broken, they were fixed immediately — regardless of how many.”